1. Field of Invention
The invention relates to a prism pole for supporting a reflective prism or other piece of passive or electrically or optically active equipment used principally in the course of surveying landforms, structures, etc, facilitating automatic taking of height measurements and providing height reference data corresponding therewith.
2. Description of Related Art
Prism poles are used in surveying to support a reflective prism or other piece of surveying equipment. Prior art prism poles, such as shown in FIG. 1, typically include a tubular housing and a height-adjustable rod that is telescopically partially resident therein. The height-adjustable rod slides inwardly and outwardly with respect to the tubular housing. Prior art prism poles typically include a numerical scale printed on the height-adjustable rod, typically marked in increments of hundredths ( 1/100) of a foot or thousandths ( 1/1000) of a meter. A reflective prism or other piece of surveying equipment attaches to the top of the height-adjustable rod. A light source or mirror may be at a remote location and serves to direct light at the prism. When the prism located on the top of the adjustable rod receives the light and divides the light according to the optical spectrum, the operator of the prism pole knows that the adjustable part of the prism pole (and the attached prism) is at a known height relative to the source of the light directed at the prism on the prism poles. A prism pole operator can manually read a height measurement from the numerical scale at a point along the height-adjustable rod. The operator typically then records the height measurement into a log book or manually enters the height measurement into a data collection device.
Prior art prism poles allow human error to interfere with accurate measurement-taking. For example, the height-adjustable rod of the prism pole may slowly slide down into the tubular housing, unbeknownst to the prism pole operator. Because the operator is unaware of the minor slippage, the operator errs in recording accurate height measurements.
Prior art prism poles are also problematic because operators often misread height measurements from the numerical scale. In addition, operators often fail to record changes in height measurements when the operator adjusts the position of the height-adjustable rod. Operators also make transposition errors when manually copying height measurements from the numerical scale into a log book or data collection device. A prism pole is needed that reduces the amount of human error that interferes with accurate measurement-taking.